Assessing the Impact of Tagging Species on the Fluxional Behavior of Protonated Methane

• Applicant: Professor Dr. Dominik Marx
• Subject Area: Theoretical Chemistry: Electronic Structure, Dynamics, Simulation
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 409795857

Protonated methane (CH5+) is an archetypal fluxional molecule where pronounced large-amplitude motion leads to so- alled hydrogen scrambling. Given the fundamental importance of this non-classical carbocation, it is intensely studied since decades up to present times. What still remains largely unexplored are interaction-induced perturbations of the large-amplitude motion due to attaching hydrogen molecules. Indeed, CH5+ has been tagged using hydrogen molecules in pioneering work of Y. T. Lee that suggested significant impact on scrambling, but without providing molecular insights. Here, the broadband infrared spectroscopy of hydrogen-tagged CH5+ including its isotopologues will be investigated. Another line of research will be devoted to ultralow temperature regimes where bosonic exchange occurs (eventually leading to "local superfluidity") when using bosonic tags such as helium-four atoms and para-hydrogen or ortho-deuterium molecules. While helium has already been shown by us to be an "innocent tag", this is not expected for para-hydrogen or ortho-deuterium which interact much more strongly. Structural tagging effects and their interplay with bosonic exchange will be studied at 1 K for CH5+ and also for CH3+ in the light of recent experimental findings. This research will be based on our recent methodological advances, notably machine learning to introduce CCSD(T) accuracy into path integral simulations.

• DFG Programme: Research Grants